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A low-dose ACTH (cosyntropin) test measures the function of the body’s HPA axis (hypothalamic-pituitary-adrenal axis). This system is made up of:
The pituitary gland makes substances known as hormones. One of these hormones is called ACTH. ACTH signals the adrenal glands , to release another hormone called cortisol. Cortisol is released during stressful situations and controls body functions such as:
Cortisol also helps the body use nutrients and respond to stress.
Doctors use the low-dose ACTH test to help diagnose a condition known as central adrenal insufficiency. They also use this test to check the pituitary gland’s function. The pituitary may not work correctly after treatment with radiation or steroids, or when a brain tumor is located near the pituitary.
For the low-dose ACTH test, the care team gives your child a low dose of a medicine called cosyntropin. It makes the adrenal glands release cortisol and other hormones into the blood. This test shows doctors how well your child’s hypothalamus and pituitary gland signal the adrenal glands to make cortisol.
Your child can eat and drink as usual before the test. Give your child their usual medicine(s) on the morning of the test unless the care team tells you not to do so.
Testing lasts about 1 hour. Have your child wear comfortable clothes. Bring activities such as books, games, or tablets that they can do during the test.
If your child starts any new medicines, contact your health care provider before they have their test.
You can stay with your child during the test. Before the test, the care team will place an IV in your child’s arm.
Your child should not have any side effects from the test.
Your child can return to normal activities after the test.
Reviewed: August 2023